The Baltimore County union. [volume] (Towsontown, Md.) 1865-1909, 1887-03-19

SEALED PROPOSALS will be received by the
County Commissioners of Baltimore and Howard
Counties at the COUNTY COMMISSIONERS
OFFICE, Ellicott City, Howard County, from
date, until
March, Gath, 1887,
at 1890 P. NJ,
At which time the bids will be publicly opened,
for A WROUGHT IRON PRATT TRUSS
BRIDGE OVER THE PATAPSCO FALLS AT
LEICESTER, on the B. and o. r. R., about two
miles south of Ellicott City and about fifty yards
from switch. Bidders must submit with their pro-
posals strain sheet and general plan, with di-
mansions of all parts, showing for each member of
each truss the total strain sustained and the d.
mansions and area of cross section also, the dead
weight assumed in the calculation and the result
ing weight of the truss. The weight of timber
shall be assumed at Al pounds per foot B. M.
GENERAL SPECIFICATIONS.-Th bridge
will be a through bridge, 1876 feet between ma
sonry the roadway to be 16 feet wide between
guards and not less than Is feet high in the clear
the distance from bridge seat to bed of stream
about 20 feet. The angle of bridge with abut-
ments, will be 764 degrees. The bridge must be
proportional to carry, in addition to its own
weight moving load of rs pounds per square
foot of flooring or 200 pounds per linear foot,
until the whole span is covered, in addition to
which each floor joist must carry $500 pounds
suspended from the centre with factor of safety
VI O ne HOOT JOlSt u Do VI 00OTRld plu6. L ne
flooring to be of white oak inches thick and not
less than nor more than 10 inches wide, laid
heart side down. All timber to be the best quality.
For wind strains the top lateral bracing shall be
proportional to resist lateral force of $50 pounds
per linear foot of span, and the bottom bracing a
lateral force of 200 pounds for each foot of span
No iron to be used less than inch when both
faces accessible for painting and 5-16 of inch
when only one face is accessible No bar iron to
ha ~ olo lafa krno lass
inch diameter.
MATERIAL.-The wrought bar iron to be
under tensile strain, as the bottom chords tension
diagonals, top and bottom laterals, pins, bolts,
&C., to be of the best quality double refined, fib-
UUU per square 1ncn. All shape iron to be OF the
best standard quality. No bar-iron shall be
strained in tension more than $1,000 pounds per
square inch. Shape under tension, as in floor
beams, not more than 5000 pounds net section.
to be strained more than 5000 per square inch,
reduced by Gordon's formula.
All iron before leaving shop to have one coat
of best metallic paint and pure linseed oil, and to
be thoroughly cieansed and free from rust and
loose scale before painting. All surfaces in con-
tact in riveted work to be painted before riveting
All planed or burned surfaces to be coated with
white lead and tallow. The bridge, after being
erected, shall receive second coat of the best
metallic paint and pure linseed OIL
Contractors to include in their bid the taking
down of the present wooden arch bridge and plac-
ing the material at some convenient point.
Contractors to state in their proposal the time
when the bridge shall be completed and ready for
travel, under forfeit hereafter to be fixed
Each bid must be accompanied by the sigma
lures of two responsible parties agreeing to go on
the bond of the contractor for double the am punt
of the contract price.
For further information apply to
VIM. II. SHIPLEY,
Superintendent of Bridges for BALTIC. county,
Morse Building, Baltimore.
Mch. ltd.